The present invention relates generally to an imaging forming apparatus, such as a xerographic system and fuser components for use in electrostatographic, including digital, contact electrostatic printing, and like apparatuses. More specifically, the present invention relates to reducing the effect of fuser oil or release agent streaks on fuser components by smoothing/camouflaging the streaks.
In a typical electrostatographic reproducing apparatus, a light image of an original to be copied is recorded in the form of an electrostatic latent image on a photosensitive member and the latent image is subsequently rendered visible by the application of electroscopic thermoplastic resin particles, which are commonly referred to as toner. The visible toner image is then in a loose powdered form and can be easily disturbed or destroyed. The toner image is usually fixed or fused upon a support, which may be the photosensitive member, or other support sheet, such as plain paper.
Thermal energy is used for fixing the toner image onto the support sheet and includes applying heat and pressure by various means, a roll pair maintained in pressure contact, a belt member in pressure contact with a roll, a belt member in pressure contact with a heater, and the like. Heat may be applied by heating one or both of the rolls, plate members, or belt members. With a fixing apparatus using a thin film in pressure contact with a heater, the electric power consumption is small, and the warming-up period is significantly reduced or eliminated.
It is important in the fusing process that minimal or no offset of the toner particles from the support to the fuser member take place during normal operations. Toner particles offset onto the fuser member may subsequently transfer to other parts of the machine or onto the support in subsequent copying cycles, thus increasing the background or interfering with the material being copied there. Such “hot offset” occurs when the temperature of the toner is increased to a point where the toner particles liquefy and the molten toner splits during the fusing operation with a portion of the toner remaining on the fuser member. The hot offset temperature or degradation of the hot offset temperature is a measure of the release property of the fuser. Accordingly, it is desirable to provide a fusing surface, which has a low surface energy to provide the necessary release. To ensure and maintain good release properties of the fuser, it has become customary to apply release agents, sometimes referred to as fuser oil, to the fuser roll during the fusing operation. Typically, these materials are applied as thin films of, for example, silicone oils to prevent toner offset.
As shown in FIG. 1, a fusing station 1 of an imaging apparatus includes a fuser roll 10 comprising a polymer surface 5 upon a suitable base member 4, a hollow cylinder or core fabricated from any suitable metal, such as aluminum, anodized aluminum, steel, nickel, copper, and the like, having a suitable heating element 6 disposed in the hollow portion thereof which is coextensive with the cylinder. The fuser roll 10 can include an adhesive, cushion, or other suitable layer 7 positioned between the core 4 and the outer layer 5. A pressure roll 20 cooperates with the fuser roll 10 to form a nip 11 through which copy paper or other substrates 8 pass such that toner images 9 contact an elastomer surface of the outer layer 5 of the fuser roll 10. The pressure roll 20 has a rigid steel core 2 with a polymer or elastomer surface or layer 3 thereon. A sump 30 contains a polymeric release agent, or fuser oil, 26 that may be a solid or liquid at room temperature, but it is a fluid at operating temperatures. The pressure roll 20 may include a heating element (not shown).
In the device shown in FIG. 1 for applying the polymeric release agent 26 to the elastomer surface of the outer layer 5, a release agent meter roll 27 and a donor roll 28 are rotatably mounted in the directions indicated by the arrows, are provided to transport the release agent 26 to the elastomer surface 5. The meter roll 27 is partly immersed in the sump 30 and transports on its surface the release agent from the sump 30 to the donor roll 28. By using a metering, or doctor blade 29, a layer of polymeric release fluid 26 can be applied initially to the meter roll 27 and ultimately to the elastomer surface 5 in controlled thicknesses ranging from sub-micrometer thickness to thicknesses of several micrometers of release fluid. The metering blade 29 can regulate the amount of release fluid 26 to be applied to the surface elastomer 5.
However, in such fusing systems if there is debris on the meter roll or the donor roll, or if there is a cut in the doctor blade, then the application of the release agent to the fusing roll can be applied unevenly which would reduce the print quality of the document.